Although attempts have been made in the past to provide automatic key duplicating machines which are suitable for unattended use by the public, usually by the insertion of a coin, so far as is known none of such prior coin actuated machines for making duplicate keys have been successful commercially.
Examples of such prior coin operated key duplicating machines are U.S. Pat. Nos. 3,358,561; 3,442,174; and 3,796,130. The mechanisms for such prior apparatus has been extremely complicated and adequate provision has not been made for assuring that the master key and the key blank are properly indexed and clamped prior to the cutting of the duplicate key.
Most prior key duplicating machines having less complicated mechanisms have not been suitable for completely automatic operation. Ideally, a customer would only need to insert a master key in one slot, insert money in another slot, and receive a duplicate key. However, most prior key duplicating machines are designed such that the keys move during the duplicating process. As a result, these machines are not easily provided with slots for the insertion of the keys.
A notable exception is U.S. Pat. No. 3,430,535 which describes a key duplicating machine constructed to receive and automatically clamp a master key and a key blank within fixed slots in the front of the machine. This convenient placement of the key slots was made possible by the design of the key duplicating components. A key follower and key cutter are mounted with a first base that is slidably mounted on four vertical corner posts. The corner posts are mounted with a second base that is slidably mounted on two horizontal support shafts. Although not very complex, this design is not the most accurate for duplicating keys since the first base is prone to wobbling as it moves up and down on the corner posts in response to edge variations in the master key.
The most accurate key duplicating machines generally include a base that pivots and slides on a single support shaft. Mounted with the pivoting base can be either the keys, as described by U.S. Pat. Nos. 3,006,255 and 4,023,464, or the key follower and key cutter, as described by U.S. Pat. No. 3,675,536. As previously mentioned, key duplicating machines that involve movement of the keys, such as the 3,006,255 and 4,023,464 patents, are not suited for completely automatic operations. Furthermore, the 3,675,536 patent, which states that the described machine is semi-automatic, has fixed key clamps that mount the keys parallel to the front of the machine within a safety cover. The clamps could not be repositioned for insertion of the keys into slots in the machine.
Additionally, the prior art has used key followers of a bar shape to engage edge variations in master keys. The bars are often adjustable for controlling the depth of cutting of the key blank to compensate for variations in the placements of the master key and key blank.